Catalysts of the aforesaid type have been described, as well as the respective methods of preparing them, in several patents. See, for instance, British Pat. No. 971,996, U.S. Pat. No. 4,124,534, British Pat. No. 1,345,653 and the pending application of Enrico Cavaterra et al Ser. No. 742,238 filed June 7, 1985 (now U.S. Pat. No. 4,587,230) which disclose the impregnation of alumina with solutions of CuCl.sub.2 and MgCl.sub.2.
In the first cases, however, i.e., British Pat. Nos. 971,996 and 1,345,653 and U.S. Pat. No. 4,124,534, no precise direction is given sufficient to obtain the high yields required by modern plants and, at the same time, a satisfactory degree of fluidization.
These results, on the contrary, can be obtained by using the catalyst according to the aforesaid Cavaterra et al application. Also in this case, however, there are drawbacks; in fact, said application teaches that excellent performances can be achieved only if the catalyst is treated with aqueous hydrochloric acid (HCl), which may involve some problems concerning the ecology and corrosion in the plant, during the catalyst preparation.